Frequency Domain Direct Sequence Spread Spectrum with Flexible Time Frequency Code
A spread spectrum radio frequency communication system includes a Forward Error Correction (FEC) algorithm to encode digital data to provide a plurality of symbol groups, the FEC algorithm using a Reed Solomon FEC code, an interleaving algorithm to map each one of the plurality of symbol groups into a corresponding one of a plurality of coherent subbands, and a Walsh encoder to encode each one of the plurality of symbol groups.
1 . A method of receiving a wireless signal comprising:
identifying a signal space for wireless communication, the signal space including a range of frequencies;
receiving a waveform in the signal space, the waveform including a preamble and the waveform organized into a plurality of sub-bands, each one of the plurality of sub-bands defined by one of a plurality of time-frequency tiles characterized by a bandwidth and an integration time;
determining the bandwidth and the integration time of each of the plurality of sub-bands based upon the preamble; and
demodulating a data signal from the waveform using direct sequence spreading for each one of the plurality of sub-bands.
2 . The method of claim 1 wherein demodulating the data signal includes using the preamble to determine at least one of an m-ary alphabet size and a data rate used to encode the data signal.
3 . The method of claim 1 wherein the preamble includes an indication of the bandwidth and the integration time of at least one of the plurality of time-frequency tiles.
4 . The method of claim 1 wherein the preamble includes an indication of one or more of an m-ary alphabet size and a data rate for at least one of the plurality of time-frequency tiles.
5 . The method of claim 4 wherein at least one of the m-ary alphabet size and the data rate vary over time.
6 . The method of claim 4 wherein the m-ary alphabet size and the data rate vary from burst to burst in a packetized data system.
7 . The method of claim 1 wherein the bandwidth and the integration time of all of the time-frequency tiles are selected to provide a plurality of channels each having a coherent time-bandwidth product.
8 . The method of claim 1 wherein all of the time-frequency tiles have a common bandwidth and a common integration time.
9 . The method of claim 1 further comprising changing at least one of the bandwidth and the integration time between a plurality of bursts of data transmission.
10 . The method of claim 1 wherein the signal space is used for ad hoc mobile network communications.
11 . The method of claim 1 further comprising descrambling the data signal with a non-linear Transmission Security (TRANSEC) pseudo-noise overlay.
12 . The method of claim 1 wherein the waveform carries the data signal at a magnitude substantially within a noise floor for the signal space.
13 . A receiver that receives a waveform in a signal space, the waveform including a preamble and the waveform organized into a plurality of sub-bands, each one of the plurality of sub-bands defined by one of a plurality of time-frequency tiles characterized by a bandwidth and an integration time, the receiver adapted to determining the bandwidth and the integration time of each of the plurality of sub-bands based upon the preamble and to demodulate a data signal from the waveform using direct sequence spreading for each one of the plurality of sub-bands.
14 . The receiver of claim 13 wherein the receiver demodulates the data signal using the preamble to determine at least one of an m-ary alphabet size and a data rate used to encode the data signal.
15 . The receiver of claim 13 wherein the preamble includes an indication of the bandwidth and the integration time of at least one of the plurality of time-frequency tiles.
16 . The receiver of claim 13 wherein the preamble includes an indication of one or more of an m-ary alphabet size and a data rate for at least one of the plurality of time-frequency tiles.
17 . The receiver of claim 16 wherein at least one of the m-ary alphabet size and the data rate vary over time.
18 . The receiver of claim 16 wherein the m-ary alphabet size and the data rate vary from burst to burst in a packetized data system.
19 . The receiver of claim 16 wherein the bandwidth and the integration time of all of the time-frequency tiles are selected to provide a plurality of channels each having a coherent time-bandwidth product.
20 . The receiver of claim 14 wherein all of the time-frequency tiles have a common bandwidth and a common integration time.